Map of island countries: these states are not located on any continent (landmass), but they are usually grouped geographically with a neighbouring continent

A map of transcontinental countries, countries that control territory in more than one continent.

Contiguous transcontinental countries.

Non-contiguous transcontinental countries.

Countries that could be considered transcontinental depending on definitions and claim legality.

The boundaries between the continents of Earth are generally a matter of geographical convention. Several slightly different conventions are in use. The number of continents is most commonly considered seven but may range as low as four when the Americas and Afro-Eurasia are each considered a single continent. According to the definition of a continent in the strict sense, an island cannot be part of any continent, but by convention and in practice most major islands are associated with a continent.

While the isthmus between Asia and Africa and that between the two Americas are today navigable, via the Suez and Panama canals, man-made diversions and canals are generally not accepted on their own accord as continent-defining boundaries; the Suez Canal happens to traverse the isthmus between the Mediterranean Sea and Red Sea, dividing Asia and Africa. The remaining boundaries concern the association of islands and archipelagos with specific continents, notably:

The European and African mainlands are non-contiguous, and the delineation between these continents is thus merely a question of which islands are to be associated with which continent.

The Portuguese Atlantic island possession of the Azores is 1,368 km (850 mi) from Europe, 1,507 km (936 mi) from Africa, and is usually grouped with Europe if grouped with any continent. By contrast, the Canary and Madeira islands off the Atlantic coast of Morocco are much closer to and usually grouped with Africa (Madeira is 860 km (530 mi) from Europe and 660 km (410 mi) from Africa).[1]

The island nation of Malta is approximately 81 km (50 mi) from the coast of Sicily in Europe - much farther than the 288 km (179 mi) distance to the closest African coast. The nearby Italian island of Lampedusa is 207 km (129 mi) from Sicily while just 127 km (79 mi) from the African coast; similarly, Pantelleria is 100 km (62 mi) from Sicily and just 71 km (44 mi) from the African coast. All are generally included within Europe if grouped with any continent at all.

The threefold division of the Old World into Europe, Asia and Africa has been in use since the 6th century BC, due to Greek geographers such as Anaximander and Hecataeus. The boundary between Europe and Asia is somewhat unique among continental boundaries because of its largely mountain-and-river-based characteristics north and east of the Black Sea. Europe can be considered more of a subcontinent within Eurasia in de facto terms, and it has sometimes been referred to as such.[2]

Anaximander placed the boundary between Asia and Europe along the Phasis River (the modern Rioni) in the Caucasus (from its mouth by Poti on the Black Sea coast, through the Surami Pass and along the Kura River to the Caspian Sea), a convention still followed by Herodotus in the 5th century BC.[3] As geographic knowledge of the Greeks increased during the Hellenistic period,[4] this archaic convention was revised, and the boundary between Europe and Asia was now considered to be the Tanais (the modern Don River). This is the convention used by Roman era authors such as Posidonius,[5]Strabo[6] and Ptolemy.[7]

Throughout the Middle Ages and into the 18th century, the traditional division of the landmass of Eurasia into two continents, Europe and Asia, followed Ptolemy, with the boundary following the Aegean Sea, the Dardanelles, the Sea of Marmara, the Bosphorus, the Black Sea, the Kerch Strait, the Sea of Azov and the Don (ancient Tanais). But maps produced during the 16th to 18th centuries tended to differ in how to continue the boundary beyond the Don bend at Kalach-na-Donu (where it is closest to the Volga, now joined with it by the Volga–Don Canal), into territory not described in any detail by the ancient geographers.

By the mid-19th century, there were three main conventions, one following the Don, the Volga–Don Canal and the Volga, the other following the Kuma–Manych Depression to the Caspian and then the Ural River, and the third abandoning the Don altogether, following the Greater Caucasus watershed to the Caspian. The question was still treated as a "controversy" in geographical literature of the 1860s, with Douglas Freshfield advocating the Caucasus crest boundary as the "best possible", citing support from various "modern geographers".[11]

In Russia and the Soviet Union, the boundary along the Kuma–Manych Depression was the most commonly used as early as 1906.[12] In 1958, the Soviet Geographical Society formally recommended that the boundary between the Europe and Asia be drawn in textbooks from Baydaratskaya Bay, on the Kara Sea, along the eastern foot of Ural Mountains, then following the Ural River until the Mugodzhar Hills, and then the Emba River; and Kuma–Manych Depression,[13] thus placing the Caucasus entirely in Asia and the Urals entirely in Europe.[14] However, most geographers in the Soviet Union favoured the boundary along the Caucasus crest[15] and this became the standard convention in the latter 20th century, although the Kuma–Manych boundary remained in use in some 20th-century maps.

Map of the world according to Anaximander (6th century BC). Only the parts of Europe, Asia and Africa directly adjacent to the Mediterranean and the Black Sea are known. The Phasis River of the Caucasus is imagined as separating Europe from Asia, while the Nile separates Asia from Africa (Libya).

In this 1570 map of Asia (Asiae Nova Descriptio), the Tanais is used as continental boundary. Moscovia is represented as "transcontinental", having an Asiatic and a European part (labelled Europae pars).

This 1719 map of "ancient Asia" (Asia Vetus) divides Sarmatia into Sarmatia Europea and Sarmatia Asiatica. The continental boundary is drawn along the Tanais (Don), the Volga and the Northern Dvina.

A German map of 1730 by Johann Christoph Homann has a similar boundary to the one shown by Moll, but following the full length of the Samara bend and then cutting across to the Irtysh directly, placing the Tobol and Tobolsk in Asia.

Though most geographic sources assign the area south of the Caucasus Mountain crest to Southwest or West Asia,[21] no definition is entirely satisfactory, with it often becoming a matter of self-identification. Cultural influences in the area originate from both Asia and Europe. While geographers rarely define continents primarily politically, Georgia and to a lesser extent Armenia and Azerbaijan are increasingly in the 21st century politically oriented towards Europe, but Armenia has a great cultural diaspora to the south, and Azerbaijan shares a cultural affinity with the Turkic countries of Central Asia.[22]

This Ural River delineation is the only segment not to follow a major mountain range or wide water body, both of which often truly separate populations. However, the Ural River is the most common division used by authorities,[18][23][24] is the most prominent natural feature in the region, and is the "most satisfactory of those (options) proposed"[25] which include the Emba River, a much smaller stream cutting further into Central Asian Kazakhstan. The Ural River bridge in Orenburg is even labeled with permanent monuments carved with the word "Europe" on one side, "Asia" on the other.[26]

There are other definitions for Europe and Asia limits, such as political definitions. The United Nations Statistics Division lists transcontinental countries under the continent in which they have the majority of their population:[28]

The Council of Europe includes the countries of Armenia, Azerbaijan, Cyprus, Georgia, Russia and Turkey. It notes that "two Council of Europe member States, Turkey and Russia, belong geographically to both Europe and Asia and are therefore Eurasian. Strictly speaking, the three South Caucasus States, Armenia, Azerbaijan and Georgia are located in Asia, yet their membership (in) political Europe is no longer in doubt." [29] Although not a member, Eurasian Kazakhstan is granted the right to request membership. [30]

Cyprus is an island of the Mediterranean located close to Asia Minor, so that it is usually associated with Asia and/or the Middle East, as in the World Factbook, but it was nevertheless admitted to the Council of Europe in 1961 and joined the EU in 2004, except for the northern part which is politically and culturally connected to Turkey, Asia.

Europe and North America are separated by the North Atlantic. In terms of associating islands with either continent, the boundary is usually drawn between Greenland and Iceland. The Norwegian islands of Jan Mayen and Svalbard in the Arctic Ocean are usually associated with Europe. Iceland and the Azores are protrusions of the Mid-Atlantic Ridge and are associated with and peopled from Europe, even though they have areas on the North American Plate. (Definitions of "continents" are a physical and cultural construct dating back centuries, long before the advent or even knowledge of plate tectonics; i.e., defining a "continent" falls into the realm of physical and cultural geography, while continental plate definitions fall under plate tectonics in the realm of geology.)

The geographical notion of a continent stands in opposition to islands and archipelagos.[31] Nevertheless, there are some islands that are considered part of Europe in a political sense. This most notably includes the British Isles (part of the European continental shelf and during the Ice Age of the continent itself), besides the islands of the North Sea, the Baltic Sea and the Mediterranean which are part of the territory of a country situated on the European mainland, and usually also the island states of Iceland and Malta.

Russia's Vaygach Island and Novaya Zemlya extend northward from the northern end of the Ural Mountains and are a continuation of that chain into the Arctic Ocean. While Novaya Zemlya was variously grouped with Europe or with Asia in 19th-century maps, it is now usually grouped with Europe, the continental boundary considered to join the Arctic Ocean along the southern shore of the Kara Sea. The Russian Arctic archipelago of Franz Josef Land farther north is also associated with Europe.

Europe ends in the west at the Atlantic Ocean, although Iceland and the Azores archipelago (in the Atlantic, between Europe and North America) are usually considered European, as is the Norwegian Svalbard archipelago in the Arctic Ocean. Greenland is geographically part of North America, but politically associated with Europe as it is part of the Kingdom of Denmark, although it has extensive home rule and EU law no longer applies there.

Historically, in Greco-Roman geography, Africa (Libya) was taken to begin in Marmarica, at the Catabathmus Magnus, placing Egypt in Asia entirely. The idea of Egypt being an "African" country seems to develop in around the mid 19th century; the term Africa was classically reserved for what is now known as the Maghreb, to the explicit exclusion of Egypt, but with the exploration of Africa the shape of the African landmass (and Egypt's "natural" inclusion in that landmass) became apparent. In 1806, William George Browne still titled his travelogue Travels in Africa, Egypt, and Syria. Similarly, James Bruce in 1835 published Travels through part of Africa, Syria, Egypt, and Arabia. On the other hand, as early as 1670 John Ogilby under the title Africa published "an accurate Description of the Regions of Egypt, Barbary, Libya, and Billedulgerid, the Land of Negroes, Guinea, Æthiopia, and the Abyssines, with all the adjacent Islands, either in the Mediterranean, Atlantic, Southern, or Oriental Seas, belonging thereunto".

Less than 2% of Egyptian population live in the Sinai, and hence Egypt even though technically transcontinental is usually considered an African country. But when discussing the geopolitical region of the Middle East and North Africa, Egypt is usually grouped with the Asian countries as part of the Middle East, while Egypt's western neighbor Libya is grouped with the remaining North African countries as the Maghreb.

The border between North America and South America is at some point on the Isthmus of Panama. The most common demarcation in atlases and other sources follows the Darién Mountains watershed divide along the Colombia-Panama border where the isthmus meets the South American continent. Virtually all atlases list Panama as a state falling entirely within North America and/or Central America.[32]

St. Lawrence Island in the northern Bering Sea belongs to Alaska and may be associated with either continent but are almost always considered part of North America, as with the Rat Islands in the Aleutian chain.

Indonesia is today more commonly referred to as one of the Southeast Asian countries, and thus simply Asian. However, the Malay Archipelago is sometimes divided between Asia and Australasia, usually along the anthropologic Melanesian line or Weber's Line. Indonesia controls the western half of New Guinea, geographically part of Australasia. The eastern half of the island is part of Papua New Guinea which is considered to be part of the Pacific. East Timor, an independent state that was formerly a territory of Indonesia, which is geographically part of Asia, is classified by the United Nations as part of the "South-Eastern Asia" block. It is expected to join the Association of Southeast Asian Nations,[33] having been involved as an ASEAN Regional Forum member since independence, and has participated in the Southeast Asian Games since 2003. Occasionally, all of the Malay Archipelago is included in Oceania, although this is extremely rare, especially as most of the archipelago lies on the Asian continental shelf.

Antarctica along with its outlying islands have no permanent population. All land claims south of 60°S latitude are held in abeyance by the Antarctic Treaty System.

The South Georgia and the South Sandwich Islands are closer to Antarctica than to any other continent. However, they are politically associated with the inhabited Falkland Islands which are closer to South America. Furthermore, Argentina, a South American country, maintains its irredentist claims on the islands. The continental shelf boundary separates the two island groups.

^E. M. Moores, R. W. Fairbridge, Encyclopedia of European and Asian regional geology, Springer, 1997, ISBN 978-0-412-74040-4, p. 34: "most Soviet geographers took the watershed of the Main Range of the Greater Caucasus as the boundary between Europe and Asia."